Radio frequency (RF) communication networks and protocols are known having remote, roaming terminals which communicate through a variety of types of communication links to host computers. Based on the overall spatial layout, response time and loading requirements of the network, different networking schemes and communication protocols have been sought so as to most efficiently regulate the communications.
Particular advantages have been identified in the use of RF communication links such as allowing remote terminals to “roam”, free from hard-wired cable connections. In basic configurations, a single host computer communicates along some hard-wired link to an RF base station which would maintain an RF communication link to a single roaming terminal. As long as the roaming terminal stays within range of the RF base station and no other roaming terminals are needed, a very simple network configuration and communication protocol can be used. However, when faced with hundreds of roaming terminals which move in and out of the range of multiple RF base stations, networking and protocol problems emerge.
To solve these problems, attempts have been made to decrease the number of base stations by increasing the base stations range; however, the range of the often battery-powered roaming terminals cannot match the increased range of the wall-socket-powered RF base stations. Moreover, by increasing the range, collisions due to propagation times also increase, slowing down the overall communication time.
Other attempts have been made to increase the number of RF base stations so as to cover the entire roaming area. Although this solves the range problems associated with a single RF base station, additional problems result. First, roaming terminals which are in an overlapping range region between RF base stations communicate with one base station but receive unwanted communication from the other. Second, each roaming terminal often receives unwanted communication from other roaming-terminals. Similarly, each roaming terminal often encounters “hidden” communications from other roaming terminals to a common base station. Because of these encounters, each roaming terminal often transmits over the “hidden” communications causing collisions.
Additionally, as the number of RF base stations increase, communication pathways from the source to destination become more and more complex. In a network with fixed spatial locations of base stations, host computers and remote terminals, these communication pathways from a source to a destination can easily be determined. In an environment in which the spatial layout of the network continually changes, however, determining the most efficient pathways becomes very difficult. This is because the most efficient pathway from a source to a destination continually changes due to: 1) the movement of the roaming terminals; 2) the relocation of RF base stations; and 3) the occasional break down of RF base stations and host computers.
Communication networks are also known which are often partially or completely disabled upon the break down of a single element of the network.
It is therefore an object of the present invention to provide a communication protocol between the base stations and roaming terminals for optimizing the utilization of the RF range of each base station.
It is a further object of the present invention to provide an adaptive communication network with inherent redundancy.
It is another object of the present invention to provide a communication protocol for use in a network of host computers, base stations and roaming terminals which is not susceptible to collisions with “hidden” communications.
It is yet another object of the present invention to provide a communication protocol which minimizes collisions in the overlapping regions of different RF base stations.